That is the incorrect sticker for a '67 model, if in fact that's what block you have??That sticker belongs to a 73 model, which match your outer cowls. Grrr.Where are you located? I think you have a Frankenmerc? I hate them.

As for number 4, I suspect spark, not fuel. The bottom Carbie fuels both 3 & 4. Even a crook/bent reed would prevent 4 from receiving fuel.

Leave plug in 4 and place a grounded (spare) plug on number 4 lead. Start motor and check spark for strength. Never start motor without pug in hole. Its starves piston, crank etc of oil, plus it will start a small fire at the back of the motor. Not a good look! Marshmallows!

One of our members AaronJ had a collection of 4 (I recall) of short shaft 650's. Perhaps he may still own a goer which he is prepared to part with? Send him a PM.If need be, I can email you his phone number.

thanks for that reply Mercmanbeen a week or two now . sorry ive done this and that done some more research yep its a frankenstien ....so its just guess work it could have a 50 hp powerhead on it ..so putting plugs for a 65 say l17v may not be right as the 70s model runs a l77v plug the timming for a 1969 650 is different from a 1972 model mine seems to be made up of parts from 67 - 73 so its trickyim across the road from the guy i bought it off . he said it had rings and a new top where the plugs go in done about 4-6 years ago buy someone out of townhence why its got good compression as i said ..it starts idols revs but only to 2 2000 rpm underload.after injecting copious amounts of carbie cleaner down carb 2 my forth plug seems to be getting fuel oil .as is wetter than before and i used a different plug so i think we are on all 4 cyliners.so this brings me to the prop . i have the original as a spare buts its stuffed ,has the numbers on it mercury original 13and ? x 15 pitch found tables with prop sizes and pitches for 65 hp from that era i cant tell what ive got on as i cant find any id numbers ..i should have a 13 .5 x 15 lets say .. different prop pitch and size for d``ifferent revs of the same engine it says that a 13 will rev to 4800-5200- but a 14 with some ?inch pitch ..which is designed to push a houseboat will rev to 2800 but have heaps of push so maybe ive got a bloody houseboat prop and nothing is wrong with my unit!so i stopped at a mercury parts shop and enquired about buy a correct prop for $200-300 willing to give it a crack and the guy says "reckon your wasting your money .youve got other issues and didnt even offer me a prop ... so i have finally decided to give it away . i give in . i cant afford to buy anew 60 at 8 grand ,but i dont want to buy somebody elses second hand 20 year old piece of that they want half the original price for out of gumtree or ebay ..ive learnt my lesson just because it starts and runs doesnt mean its a good outboard a friend of a friend ended up being a mercury outboard expert . he loaned me the flywheel remover and a compression tester small enough to get to no 4 plug comp is good all 4 around 120 psi and even anyway stuck with a no go boat ..thinking of giving back to the guy i bought it off ($1000.00) and and telling him to keep his money and have his boat as im over it luckely it was more time than money spent lessons learnt

Not only could the prop be a factor, you may have a gearbox with the incorrect ratio based on what ever powerhead you have. Sent us a pic of the gearbox plus the midsection and shockers (if any). These pics will assist me in figuring out the possibilities.

Hi . great thinking and good theory sbut being the fact that i have video of this engine wot and up on a plane ,3 minutes before it stopped it coughed a bit ran a bit and coughed and died . which we have found out to be the flywheel spinning and shearing the key. no start again and i dont think it sheared the key due to a sudden lock up stop !i died slowly so i asume it was due to incorrect torque setting on flywheel nut .not tight enoughand the guy i bought it off ran it in this configuration before me . with this prop ...he did admit that i didnt go as hrd as it did after i tinkered and lubed the dizzy magnito thing ( 1 st post )so ill push reset ( wish there was one ).and go back to the start .chapter 1 page 1 and with a fresh head check voltages . sparks . can now check timing in gear at idle ( im suspecting timing still rememering 2 mechanics have both suspected timimg )i l do a link and sink checking that mercaman thanks for your input .. im working on a 4-6 deg atdc idle 38deg ithink wotbut other ignition setting for like wise engines seem to be all btdc?the plugs firing before it reached tdc understanding it advances as the revs increase to pre anticipate the the next time to fire but still weird some are before .and a few are after ..or am i wrong and my timng settings are wrong and sorry mercman there is no showcase or mercedes benz after this quiz if you win , but i will sell you my 1969 280s ( 2 50 year old headaches that both start with m)

The loom in your most recent picture doesn't look real flash. It shouldn't look limp like that (near the support bracket).Take the electrical tape off and look for perished/damaged insulation of the wires within the loom.Can you borrow another control box and loom assembly from someone? (I had spare control boxes up until this time last year.) Try speaking to Guy at the Outboard Workshop - Carrum Downs. I sold most of my collection to him.

This is an obvious one... is the vent on the fuel tank open, since attending to all the other suspects?

The other thing I see in the pic.. That's not a 1967 outer. This leads me to think the position of timing mark (decal) is probably not matched to your powerhead. This needs further investigation, only if there is nothing wrong with the wiring within the loom.

I've read everything and you've gone around in one big circle. Need to start from basics again. Mercman's point about mis-matches needs to be kept in mind, it may or may not be contributing to the problem.

Have you checked number one cylinder piston top dead centre to see if it matches the TDC on the label before checking ignition timing? Timing should be checked at max advance which is 32 degrees for a 1967 model. Can be checked at any revs or static.

Don't let a clean spark plug on the bottom cylinder mislead you either, some in-line Mercury's do that.

If you had a houseboat prop on it, it would be revving its head off and getting no-where, not loading up.

Obviously you are using a good brand of fuel like BP and a quality 2 stroke oil like Mercury premium plus or Evinrude XD30.

I would think a 15 pitch prop is not too big, your gearbox should be a 2.1-1 ratio.

When under full load, have you had anyone squirt some fuel in to the carburetors to check for fuel starvation?

Can you post a photo of the spark plugs, so Mercman and I can see them.

thanks -Austral,Mercman and thanks Mark Water in the plugs would mean .. in the water at dock reving to 3-4000rpm waterpump pumping hard would maybe give me ,missing or lumpy rpm ..not getting that . it revs clean to 4800 under no load ..( i may be wrong )in the first week- i opened a can of worms by opening controller , total re wire as it was all stuffed . water had got in through choke button and all the wire had perished and corroded . all redone .tested from controller to conections inside the engine therefor testing the loom and black external plug and internal wiring loom for continuity and voltage with a multi meter .but i will check that loom end again vent checked...... i recon every time i try it ( isnt that the first sin ?)timing mark lines up and piston top dead center .. visited that at the time of the flywheel re install and yep ill re check thatMarks correct.the houseboat prop would still rev ..i didnt read some pdf i found correctly. Information overload no havent squirted fuel in under load ... and im using good fuel and oil ..had 91octane and tried 95 .( which is better?) i have not tested in the water for 3 weeks. so i should try it again before i pull it all apart i have missed something. ive just got to find it

sunday morning .bays flat .slipped it in. idle , out trim it in.....go ! up .up up . slowley revs increase .and we are now ....plaining check tacho , 2800 2900 3000 3100..wot played around with trim and had me and mate jumping around up front trying to increse rpm by weight distributionbut moving and plaining But it was fun ! finally after 1 year i got it to move along aadd some chop and swell and its probably back to useless again! but is is a positive .(Frankenstien phsyco engine ...gives you a little bit of improvement just to keep you hooked )all it had to do was rev to over 4000 rpm under load !and i would have spent money replacing any part with any new parts i could find on the web .slowley week by week .Im thinking now ,, becuase i fixed it this far ..of finding another mechanic drop it off and say nothing of my past history" i was out last sunday mate and its was not reving over 3000 rpm ..strange hey " and leave it with him

used it a few times .dreaming of a new outboard 4 stroke @ 9100.00 just goto come up with the cash also decided to get new stator . under flywheel ,new internal loom and new leads and boots cost around $600 all cdi if it doesnt fix it ill replace the switch box with cdi replacement around $300 .timings good link and sink goodstill reving max at 3100 and plaining, so im chasing 2000 rpm .( have voltage fluctuation up and down )have two rectifiers and both ok so ?gets me out and back at the moment so im content , at least i have caught a fish .time has come to start throwing some dollars at it ( parts not mechanics )